Apple has determined that under certain circumstances the rubber surface on some MacBooks may separate from the bottom case of the system. MacBooks shipped between October 2009 and April 2011 may experience this issue.
Apple will replace the bottom case of any affected MacBook, free of charge, that exhibits the issue. You can see details of the program at Apple’s page about the program.
If your White, Plastic Uni-Body Macbook has this issue, you can stop by any MacMedics office and we can replace the bottom case via Apple’s replacement program free of charge. No appointment is necessary, just stop by. The repair takes about 10 minutes.